Mechanical efficiency of chain drive vs roller drive

mifletz

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Aug 25, 2009
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The road surfaces in N.Israel are so poor that my chain drive threw its chain three times too often. So I've gone back to friction drive for the moment. Although less power, friction drive is much more sturdy and reliable and tolerant of bumps. Having changed to semi-slicks has also helped considerably. I await to read a proper review of Staton's new axle kit before considering going back to a chain.
 


mifletz

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Aug 25, 2009
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They're thread-on freewheel sprockets. An example of a shimano freewheel sprocket is shown below. They're designed to thread on 1-3/8 inch, 24 TPI hub. Staton makes several freewheel adapters, to allow you to mount a freewheel to a shaft. His adapters can be used on shaft sizes ranging from 5/8 inch through 1 inch. Available sprocket sizes for this thread-size range from 16 teeth, up through 22 teeth, and I believe I remember seeing a few 25 tooth ones. There are also similar, thread-on freewheels with a flange, so you can bolt larger sprockets up tp them.

Here's a link to his 3/4 inch adapter.

There's another, me(ric standard thread-on freewheel, which threads onto 30mm X 1mm thread spacing, which allows smaller sprocket sizes. (as few as 13 teeth)

This is my sprocket









Is my sprocket amenable to changing to a freewheeler
like this one you mentioned?

 
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loquin

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Jan 11, 2008
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The spline on the gearbox shaft is the issue. (Dimensions below.)

It's very difficult to find a matching coupling, (at least in the U.S.) The simplest approach would be to sacrifice a drive sprocket. If the existing sprocket 'barrel' is greater than 1.375 inch in diameter, you could get it turned down, then cut 1-3/8, 24 TPI threads into it, to form a freewheel adapter.

Or, turn it down to 3/4 or 7/8 inch diameter, then get one of Staten's adapters.

Or, simpler yet, you could buy a 1/2 inch shaft adapter from Staten, bore it out to 14mm, and mount it to the shaft, using the setscrew to lock it into place. (You should also be able to machine (or file/grind) the key so that it will fit the now slightly shallower 1/8th inch key way in the adapter, but also fits into one of the 6 slots in the shaft...) If needed, the amount of material removed would be very small (between one and two tenths of a millimeter) from the setscrew face of the key. Plus, a small amount would need to be ground or filed from the corners of the key inserted into the spline side of the key. (ref the modified key cross section, below)
 

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loquin

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Note that these freewheel sprockets use chain with a half inch pitch. So, you would probably need to replace the rear sprocket as well. Since the sprocket teeth are also longer, this chain size may be less susceptible to jumping the sprocket. You should also make sure that the chain is snug, using an idler sprocket.

Edit: Staton apparently doesn't sell 1/2 inch adapters. So, you would need to use the 15mm metric version, and shim it with .5 mm shim stock, or the 5/8 adapter, and shim it with shim stock totaling about .94 mm. The 15mm version uses 4mm key stock, which you would need to obtain, and file to fit. The 5/8 inch inch version uses 3/16 inch key stock, which would need similar filing (on a larger scale,) to fit.

While the 15mm metric version has two thumbscrews, it is longer than the 5/8 inch version, and may be too long to fit on the splined shaft of the gearbox. On the positive side, you should be able to easily find shimstock in exactly 0.5mm thickness...
 
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mifletz

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Aug 25, 2009
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For what purpose are these expensive little freewheeling sprockets used for apart from on a few motorised bicycles?!
 

GearNut

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It will ratchet freely and reduce the effort required to pedal the bike when the engine is not running. This is because all of the associated transmission components from the clutch to the transmission sprocket will not be forced to turn with the rotation of the chain.
Also, when traveling downhill, if the speed of the bicycle exceeds the normal operating speed of the engine and transmission, the freewheel will act as a safety clutch of sorts and free spin instead of forcing the engine and transmission to spin faster then they were designed to. It also makes casual coasting easier. You do not have to let the automatic clutch slow down to it's stall speed before the clutch shoes disengage from the clutch bell.
 

mifletz

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Aug 25, 2009
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Have you a photo of your bike with a freewheel sprocket?


What size chain does it use? If you swap out the drive sprocket with a freewheel, you could coast with the engine idling... (very little drag with just the chain /driven sprocket turning.)
 

donutguy

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Mar 8, 2010
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I have the Mitsubishi TLE 43 friction drive kit from Staton. I use the 1 1/2 inch roller and after it was broken in- I get close over 35 mph on flat ground.

That's fast enough for me!

I went with the friction drive kit for a few reasons....

-It's very easy to transfer between bikes

-It quite a bit easier changing flat tires

-It is somewhat less conspicuous then a frame mounted motor- the less attention I draw from the authorities-the better.

-It can easily be disengaged if I have motor issues and be pedaled home.

-I use a large 2.4 inch tire for maximum roller contact.

The main disadvantage-it doesn't work for **** in the wet....but unless I get caught in a rain storm-no biggie as I mainly ride it for recreation.
 

GearNut

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My daughter has a pocket bike that uses that exact transmission and #25 chain size. The freewheel is on the rear wheel instead of the transmission. I have yet to see a freewheel that mounts on this type of transmission.
 
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